my_plus(0,X,X):- natural_number(X).
my_plus(s(X),Y,s(Sum)):-
    my_plus(X,Y,Sum).
    
le(0,X):-natural_number(X).
le(s(X),s(Y)):-
    le(X,Y).
    
times(0,X,0):- natural_number(X).
times(s(X),Y,Z):-
    my_plus(Y,Z1,Z),times(X,Y,Z1).
    


    
    
    


natural_number(0).
natural_number(s(X)):-
    natural_number(X).


